The present invention relates to the field of micro mechanical or micro electro mechanical devices such as ink jet printers. The present invention will be described herein with reference to Micro Electro Mechanical Ink jet technology. However, it will be appreciated that the invention does have broader applications to other micro mechanical or micro electro mechanical devices, e.g. Micro electro mechanical pumps or micro electro mechanical movers.
Micro mechanical and micro electro mechanical devices are becoming increasingly popular and normally involve the creation of devices on the xcexcm (micron) scale utilizing semi-conductor fabrication techniques. For a recent review on micro-mechanical devices, reference is made to the article xe2x80x9cThe Broad Sweep of Integrated Micro Systemsxe2x80x9d by S. Tom Pickaxe and Paul J. McWhorter published December 1998 in IEEE Spectrum at pages 24 to 33.
One form of micro electro mechanical devices in popular use are ink jet printing devices in which ink is ejected from an ink ejection nozzle chamber. Many forms of ink jet devices are known.
Many different techniques on ink jet printing and associated devices have been invented. For a survey of the field, reference is made to an article by J Moore, xe2x80x9cNon-Impact Printing: Introduction and Historical Perspectivexe2x80x9d, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207 to 220 (1988).
Recently, a new form of ink jet printing has been developed by the present applicant, which is referred to as Micro Electro Mechanical Inkj et (MEMJET) technology. In one form of the MEMJET technology, ink is ejected from an ink ejection nozzle chamber utilizing an electro mechanical actuator connected to a paddle or plunger which moves towards the ejection nozzle of the chamber for ejection of drops of ink from the ejection nozzle chamber.
The present invention concerns improvements to a mechanical bend actuator for use in the MEMJET technology or other micro mechanical or micro electro mechanical devices.
There is disclosed herein a mechanical actuator for micro mechanical or micro electro mechanical devices, the actuator comprising:
a supporting substrate,
an actuation portion,
a first arm attached at a first end thereof to the substrate and at a second end to the actuation portion, the first arm being arranged, in use, to be conducively heated,
a second arm attached at a first end to the supporting substrate and at a second end to the actuation portion, the second arm being spaced apart from the first arm, whereby the first and second arms define a gap between them,
at least on strut interconnecting the first and second arms between the first and second ends thereof, and
wherein, in use, the first arm is arranged to undergo expansion, thereby causing the actuator to apply a force to the actuation portion.
Preferably the first arm comprises:
a first main body formed between the first and second ends of the first arm;
a first tab extending from the first main body; and
wherein a first one of the at least one strut interconnects the tab with the second arm.
Preferably the second arm comprises:
a second main body formed between the first and second ends of the second arm;
a second tab extending from the second main body; and
wherein the first one of the at least one strut interconnects the first and second tabs.
Preferably the first and second tabs extend from respective thinned portions of the first and second main bodies.
Preferably the first arm comprises a conductive layer that is conducively heated to cause, in use, the first arm to undergo thermal expansion relative to the second arm thereby caused the actuator to apply a force to the actuation portion.
Preferably the first and second arms are substantially parallel and the strut is substantially perpendicular to the first and second arms.
Preferably a current is supplied in use, to the conductive layer through the supporting substrate.
Preferably the first and second arms are formed from substantially the same material.
Preferably the actuator is manufactured by the steps of:
depositing and etching a first layer to form the first arm;
depositing and etching a second layer to form a sacrificial layer supporting structure over the first arm;
depositing and etching a third layer to form the second arm; and
etching the sacrificial layer to form the gap between the first and second arms.
Preferably the first arm comprises two first elongated flexible strips conducively interconnected at the second arm.
Preferably the second arm comprises two second elongated flexible strips.
Preferably the actuation portion comprises a paddle structure.
Preferably the first arm is formed from titanium nitride.
Preferably the second arm is formed from titanium nitride.